In general, since the water-insoluble mineral has a high specific gravity of usually 1.5 or more, the water-insoluble mineral is easily precipitated in water. Therefore, in order to stably disperse the water-insoluble mineral in water, it is necessitated that the water-insoluble mineral is firstly made into fine particles.
As to methods for making the water-insoluble mineral into fine particles, there have been generally known physical crushing methods using a ball mill or jet mill. However, in this method, there is a limitation in obtaining fine particles having a particle size in the order of several microns, so that it is made impossible to stably disperse the fine particles in water.
As to methods for preparing fine particles having particle sizes in the order of submicrons, which are even smaller than those of the fine particles described above, there have been numerously reported chemical production methods utilizing reactions for forming salts by neutralization. According to this method, there can be produced ultrafine particles having a particle size of 1/100 microns. However, the resulting ultrafine particles are immediately formed into secondary agglomerates after its formation, so that there poses a problem in forming coarse particles having particle sizes in the order of microns.
In order to eliminate this problem, there have been proposed methods for adsorbing and retaining primary fine particles in the three-dimensional, network structure of crystalline cellulose or mucopolysaccharides by adding the crystalline cellulose and the mucopolysaccharides in water (Japanese Patent Laid-Open No. Sho 56-117753 and Japanese Examined Patent Publication No. Sho 57-35945); and methods of alleviating specific gravity by, when adding a water-insoluble mineral to fats and oils and dispersing the water-insoluble mineral therein, adjusting the content of the fats and oils in the resulting mixture so as to have the content to be 30% by weight or more (Japanese Patent Laid-Open No. Sho 57-110167). In any of these methods, however, since it is needed to contain large amounts of the substances other than the targeted water-insoluble mineral, there are defects in that the solute dispersed therein is diluted, and that the dispersibility of the water-insoluble mineral becomes drastically poor.
As to methods for eliminating the above defects, there have been developed a method for treating surfaces of fine particles of a water-insoluble mineral with an organic acid or an alkalizing agent (Japanese Patent Laid-Open No. Sho 61-15645); a method for adsorbing a surfactant, such as sucrose ester, to surfaces of fine particles of a water-insoluble mineral (Japanese Patent Laid-Open Nos. Sho 63-173556 and Hei 5-319817), and the like. In the former method, however, there is a defect in that the metal ions constituting the water-insoluble mineral are likely to be made into free ions in the water phase. In addition, in the latter method, there are defects in that the surfactant layer formed by adsorption to the surfaces of fine particles of a water-insoluble mineral is peeled off by heating for sterilization, and that secondary agglomeration of the fine particles takes place.
Incidentally, in general, there are many minerals as nutrients having low absorptivity when taken intracorporeally. Also, there are various defects in that those minerals having good absorptivity when taken intracorporeally have coloration, odors, or flavors, or those minerals may be easily reacted with other ingredients in food, and that irritability against mucous membranes of digestive tracts. For instance, as iron supplements, Japanese Patent Laid-Open Nos. Sho 63-276460, Hei 3-10659, Hei 5-49447, and Hei 7-170953 disclose iron porphyrin, ferritin, or lactoferrin, each of which is a natural-occurring iron material. However, since those iron materials have coloration and distinctive flavors, their applications to food are limited. In addition, since these nutrients are obtained by extraction from particular organs, there poses a problem in that mass production cannot be achieved owing to the necessity of complicated processes for its extraction.
Objects of the present invention are to provide a mineral composition having high thermal stability and excellent dispersibility without requiring large amounts of crystalline cellulose or fats and oils to be added to the water-soluble mineral, and food comprising the same.
Another objects of the present invention are to provide a mineral composition having high absorptivity when taken intracorporeally, substantially no coloration, odors, flavors, low reactivity with other ingredients in food, and small irritation against mucous membranes of digestive tracts, and food comprising the same.
These and other objects of the present invention will be apparent from the following description.